text: The Mesozoic is well known for its distinct Ocean Anoxic Events (OAEs) which resulted in the burial of layers of black shale. Although these OAEs are not stand alone evidence for euxinia, many do contain biomarkers which support euxinic formation. Again, evidence is not universal. OAEs may have spurred the spread of existing euxinia, especially in upwelling regions or semi-restricted basins, but photic zone euxinia did not happen everywhere.